<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>

    <!--'use strict'; 严格检查模式 避免随意性导致产生的问题-->
    <script>
        'use strict';
        //局部变量用 let
        let i = 1;


    </script>

</head>
<body>

</body>
</html>